UNIVERSITY  OF  CALIFORNIA  PUBLICATIONS. 

COLLEGE  OF  AGRICULTURE. 

AGRICULTURAL  EXPERIMENT  STATION 

BERKELEY,  CALIFORNIA. 


THE  CALIFORNIA  TUSSOCK-MOTH 


By   W.    H.    VOLCK 


The  tussock-moth  larva,  the  so-called  horned  caterpillar.    (Somewhat  enlarged.) 


BULLETIN    No.    183. 

(December,  1906.) 


W.    W.    SHANNON. 


SACRAMENTO: 

:  SUPERINTENDENT    STATE    PRINTING. 

1907. 


W.ix    IDE  WHEELER,  PhD.,  LL.D.,  P,  esident  of  the  University, 

EXPERIMENT  STATION  STAFF. 

E.  J.  WICKSON,  M.A.)  Acting  Director  and  Horticulturist. 

H.  W.  HILGARD.  Ph.D.,  LL.D.,   Chemist, 

W.  A.  SETCHELL.  Ph.D..  Botanist. 

ELWOOD  MEAD,  M.S.,  C.E.,  Irrigation  Engineer. 

C.  W.  WOODWORTH,  M.S.,  Entomologist.  [sent  on  leave.) 

R.  H.  LOUGHRIDGE,  Ph.D.,  Agricultural  Geologist  and  Soil  Physicist.     (Soils  and  Alkali.)    (Ab- 

M.  E.  JAFFA.  M.S.,  Nutrition  Expert,  in  charge  of  the  Laboratory  of  Agricultural  Chemistry  and 
■  Poultry  Station. 

G.  W.  SHAW.  M.A.,  Ph.D.,  Agricultural  Technologist,  in  charge  of  Cereal  Station. 
GEORGE  E.  COLBY,  M.S.,  Chemist.     'Fruits,  Waters,  Insecticides.) 

RALPH  E.  SMITH,  B.S.,  Plant  Pathologist  and  Superintendent  of  Southern  California  Pathological 
Laboratory  and  Experiment  Station. 

A.  R.  WARD,  B.S.A.,  D.V.M.,  Veterinarian  and  Bacteriologist. 

E.  W.  MAJOR,  B.Agr.,  Animal  Industry. 

F.  T.  BIOLETTI,  M.S.,  Viticultunst.     (Grapes,  Wine,  and  Zymology) 
H.  M.  HALL,  M.S.,  Assistant  Botanist. 

H.  J.  QUAYLE,  A.B.,  Assistant  Entomologist. 

JOHN  S.  BURD,  B.S.,  Chemist,  in  charge  of  Fertilizer  Control. 

C.  M.  HAKl~SG,  D.V.'M.,  Assistant  Veterinarian  and  Bacteriologist. 
E.  H.  SMITH,  M.S.,  Assistant  Plant  Pathologist. 

R.  E.   MANSELL,  Assistant  in  Horticulture  in  charge  of  Central  Station  Grounds. 

G.  R.  STEWART,  Assistant  in  Station  Laboratory. 

,  Assistant  in  Soil  Laboratory. 

RALPH  BENTON,  B.S.,  Assistant  in  Entomology. 

LUDWIG  ROSENSTEIN,  Laboratory  Assistant  in  Fertilizer  Control. 
ALFRED  TOURNIER,  Assistant  in   Viticulture. 
HANS  HOLM,  Student  Assistant  in  Zymology. 
A.  J.  GAUMITZ,  Assistant  in  Cereal  Laboratory. 
J.  C.  BRADLEY,  A.B.,  Assistant  in  Entomology. 

D.  L-  BUNNELL,  Clerk  to  the  Director. 


JOHN   TUOHY, /W*«,      >      Tulare  Substation,  Tulare. 

J.  T.   BEARSS,  Foreman,    ) 

J.  W.  MILLS,  Horticultural  Assistant  in  Southern  California,  Riverside. 

J.  W.  ROPER,  Patron,  )      University  Forestry  station,  Chico. 

}-..  C.  MILLER  In  charge,         ) 

ROY   JONES,  Patron,  (      Unjversity  Forestry  Station,  Santa  Monica. 

INGHAM,  Foreman,      ) 

'J    J    HUNTLEY,  Foreman  of  California  Poultry  Experiment  Station,  Petaluma. 

The  Station  publications  (Reports  and  Bulletins),  so  long  as  avail- 
able, will  be  sent  to  any  citizen  of  the  State  on  application. 


THE  CALIFORNIA  TUSSOCK-MOTH. 

(Hemerocampa  vetusta  Boisd.) 


Introductory  Note  -It  has  often  been  remarked  that  when  an  insect  like  the  codling- 
moth  produces  considerable  injury,  orchardists  are  very  prone  to  class  all  manner  of 
injury  to  this  fruit  to  this  one  cause.  The  injury  done  to  apples  and  apple  trees  by  the 
tussock-moth  hardly  resembles  the  work  of  the  codling-moth  in  any  particular,  still 
it  is  very  commonly  so  classed.  The  present  study  is  the  first  extended  account  of  the 
economics  of  our  Western  tussock-moth.  This  insect,  which  is  the  only  representative 
of  its  family  in  California,  differs  from  other  caterpillars,  including  its  nearest  Eastern 
allies,  in  its  remarkable  tolerance  of  arsenical  poisons. 

C.  W.  Woodworth. 

PRELIMINARY    STUDIES. 

The  tussock-moth  caterpillar  affecting  apple  trees  in  the  Pajaro 
Valley  was  brought  prominently  to  the  attention  of  the  Experiment 
Station  during  the  first  season  of  the  codling-moth  investigation  in  the 
spring  and  summer  of  1903,  and  considerable  attention  was  given  to  it, 
including  certain  experiments  by  Mr.  Clarke,  who  was  then  in  imme- 
diate charge  of  the  investigation  in  this  valley. 

It  was  then  noted  that  the  paris  green  spraying,  as  conducted  for  the 
control  of  the  codling-moth,  did  not  destroy  these  larvae.  Mr.  Clarke 
found  that  caterpillars  of  this  species  inclosed  in  a  cage  with  thoroughly 
sprayed  leaves  were  able  to  develop,  going  through  their  normal  trans- 
formation to  full  maturity,  and  finally  laying  eggs  in  an  apparently 
normal  manner. 

In  the  spring  of  1904,  Mr.  C.  H.  Rodgers,  the  Horticultural  Com- 
missioner of  Santa  Cruz  County,  sprayed  trees,  using  the  Kedzie 
formula  as  given  in  Bulletin  No.  155  of  this  Station,  as  a  special 
experiment  to  aid  us  in  determining  its  efficiency  as  a  control  for  the 
tussock-moth.  The  spraying  was  done  in  a  most  thorough  manner 
and  frequent  observations  were  made,  as  in  the  previous  year.  Some 
of  the  caterpillars  were  inclosed  in  a  jar  and  fed  on  thoroughly  sprayed 
leaves  only.  Neither  the  insects  on  the  trees  nor  those  inclosed  in  the 
jar  seemed  to  be  materially  affected  by  'the  poison  and  succeeded  in 
developing  into  the  adult  moths. 

During  that  season  the  insects  prospered  rather  better  than  usual  and 
it  was  noted  that  an  unusually  large  number  of  egg  masses  had  been 
deposited  on  the  trees  in  many  of  the  orchards.  Noting  this  condition 
and  because  of  the  failure  of  the  spraying  experiments,  Mr.  Rodgers 


192 


UNIVERSITY   OF    CALIFORNIA— EXPERIMENT   STATION. 


advised  the  orchardists  to  rely  on  the  older  "hand-picking"  method — 
gathering  the  egg  masses  as  thoroughly  as  possible  during  the  winter 
and  destroying  them. 

Mr.  Rodgers  and  one  or  two  orchardists  carried  out  this  program, 
collecting  large  quantities  of  the  eggs.  As  had  been  anticipated,  the 
tussock-caterpillars  became  a  serious  pest  in  1905  and  wrought  thou- 
sands of  dollars'  damages  to  the  apple  crop;  but  where  the  egg  masses 
had  been  very  carefully  picked  off  the  injury  was  not  excessive,  although 
rather  too  severe  to  be  viewed  with  equanimity. 

The  serious  injury  wrought  in  orchards  where  the  eggs  had  not  been 
picked  off  led  many  more  of  the  orchardists  to  apply  this  method 
thoroughly  during  the  winter  season  of   1905  and  1906. 

In  all  there  were  at  least  fifty  orchardists  who  went  over  the  trees  at 
least  once,  and  several  picked  them  off  two  or  three  times.  Others 
were  content  to  instruct  the  pruners  to  remove  such  of  the  egg  masses 
as  they  could  discover.  In  the  latter  part  of  May,  1906,  we  had  several 
hundred  apples  of  the  Bellflower  and  Newtown  Pippin  varieties  picked 
off  indiscriminately  in  orchards  where  egg  picking  had  been  done 
thoroughly,  and  also  in  unpicked  orchards  near  by  for  a  check.  These 
orchards  were  of  course  in  the  badly  infested  section,  and  those  selected 
as  check  orchards  were  in  each  case  the  one  most  nearly  comparable 
with  the  other  with  which  it  is  contrasted. 

It  will  be  seen  by  referring  to  the  table  that  the  average  percentage 
of  injured  apples  in  the  egg-picked  orchards  was  23.5  per  cent,  as 
against  65.6  per  cent  in  those  unpicked;  or  a  saving,  due  to  picking,  of 
42  per  cent.  Where  a  good  crop  is  obtained,  this  saving  means  a  con- 
siderable profit  on  the  investment  required  to  remove  the  eggs. 


EGG-PICKED. 


NOT  EGG-PICKED. 


Orchard. 


Crop 


No  Times 
Picked. 


Per  Cent 
of  Injury. 


Orchard. 


Crop. 


Per  Cent 
of  Injury. 


A.  v.  Jadd... 

Sanborn  

C.  H.  Rodgers 
C.  H.  Rodgers 
C.  Gr.  Redman 


Average 

Saving  due  to  picking. 


good 
light 
fair  . 
fair  . 
fair  . 


31 
27 
L6 
16 
26 


Campbell 

R.  W.  Eaton* 
W.  H.  Wiley. 


light 
good 


23.5 
42 


Average 


76 

58 
63 


65.6 


*Not  picked  until  too  late. 

The  table  also  shows  that  carefully  going  over  the  trees  two  or  three 
times  is  productive  of  good  results;  indeed,  it  is  the  last  few  egg  masses 
that  count.  The  two  orchards  of  C.  H.  Rodgers  were  perhaps  the  most 
carefully  picked  of  any  in  the  valley,  while  adjoining  orchards  not  egg 
picked  Lost  over  50  per  cent.  These  orchards  of  Mr.  Rodgers  average 
12  percent  better  than  those  where  the  picking  was  less  thoroughly  done. 


V2 


pW^Ce^-m 


M 


FIG.  1.    Defoliation  of  Bellflower  trees  by  tussock-moth  larvse,  first  the  tops  and  then 

the  whole  tree. 


194 


l   NIYFRS1TY    OF    CALIFORNIA  — EXPERIMENT   STATION 


DISTRIBUTION. 

The  tussock  caterpillar  is  very  thoroughly  distributed  over  the  Pajaro 
Valley  and  the  adjoining  hill  sections.  It  also  occurs  over  the  greater 
portion  of  California.  In  the  Pajaro  Valley,  while  it  is  to  be  found 
everywhere,  it  varies  greatly  in  abundance,  and  during  the  last  three 
seasons  its  worst   ravages  were  confined  to  certain  definite  areas.     In 


FIG.  2.    Complete  defoliation  by  the  tussock-moth  larvae, 


1891  to  1892,  according  to  Mr.  A.  X.  Judd,  in  a  limited  area,  known 
the  Blackburn  orchard,,  the  trees  were  defoliated  and  surrounding 
places  were-  also  badly  infested.  Something  then  greatly  reduced  the 
number?  of  this  insect  until  it  was  hardly  noticed;  but  in  1908  they 
again  appeared  in  destructive  numbers  in  the  original  locality,  as  well 
vera]  other  areas,  mostly   in  the  older  orchards,  and  especially 


THE   CALIFORNIA   TUSSOCK-MOTH. 


195 


near  town  and  toward  the  beach.  These  areas  are  surrounded  by  a 
widening  circle  of  less  serious  infestation.  If  the  increase  continues 
most  of  the  lightly  infested  areas  will  be  in  very  bad  condition  next 
season,  and  the  general  infestation  much  more  evident. 

FOOD    PLANTS. 

This  caterpillar  is  commonly  found  on  the  live  oak  and  the  yellow 
perennial  lupin  {Lupinus  arboreus)  that  grows  along  the  beach.  In 
the  orchard  it  feeds  on  apple  and  cherry  trees,  and  when  very  abundant 
is  found  feeding  on  walnut  and  numerous  other  plants;  but  apparently, 
in  such  cases,  these  insects  have  wandered  from  their  original  food  plant. 

On  the  lupins  at  the  beach  the  egg  masses  do  not  hatch  as  early  as 
in  the  orchards;  in  fact,  the  larvae  are  often  abundant  in  this  locality 
in  August  and  September,  which  would  bring  some  of  the  hatchings  as 
late  as  June. 

LIFE    HISTORY    AND    HABITS. 

There  is  one  generation  of  the  tussock-moth  caterpillar  a  year.  The 
moths  which  emerge  in  May,  June,  and  July  deposit  eggs  that  do  not 
hatch  until  the  following  spring.  The  caterpillar  requires  from  forty- 
five    to  sixty  days    for     its   development,   varying    according   to    the 


•     1:  |B 

&-!*    : 

;     i 

FIG.  3.  Form  of  breeding  cage 
found  preferable  for  rearing  tus- 
sock-moth larvae. 


FIG.  4.  Another  form  of 
breeding  cage  used  in 
these  experiments. 


temperature  and  sex.  The  females  require  a  longer  time  to  reach  the 
spinning-up  stage  than  the  males,  and  are  also  much  larger.  The 
tussock-moth  larva  molts  or  changes  its  skin  four  times  in  the  course  of 
its  development.  This  makes  five  larval  stages,  and  at  the  end  of  the 
fifth  stage  the  adult  larva  spins  a  cocoon,  composed  of  silk  and  the 
hairs  which  cover  the  body.     These  cocoons  are  not  very  strong,  but 


196 


i    MYKKSITY    OF    CALIFORNIA  — EXPERIMENT    STATION. 


entirely  surround  the  larva  and  afford  a  good  degree  of  protection  to 
the  insect  during  the  pupa  stage.  Shortly  after  spinning  the  cocoon 
the  last  larval  skin  is  shed  and  the  pupa  stage  begins.  In  from  sixteen 
to  twenty-seven  days  from  this  molt  the  adult  moth  emerges.  Fertil- 
ization ordinarily  takes  place  at  once,  and  within  three  or  four  days 
the  female  deposits  its  eggs. 

In  order  to  carefully  follow  this  development  and  determine  accu- 
rately the  time  required  for  the  various  stages,  a  number  of  newly 
hatched  larvae  were  placed  in  breeding  cages  in  the  laboratory  and  also 
in  muslin-bag  cages  which  were  tied  over  small  branches  in  the  orchards. 

The  cages  found  most  satisfactory  for  use  in  the  laboratory  were  con- 
st rueted  of  glass  and  cardboard,  in  such  a  way  that  the  water  given  off 


FIG    5.     Cloth  bags  used   as   breeding  cages  in   the 
orchards  in  the  study  of  the  tussock-moth  larv;e. 

by  the  living  twig  placed  within  it,  could  readily  escape,  thus  main- 
taining a  fairly  normal  atmosphere.  The  twig  was  kept  fresh  by  a  small 
bottle  of  water  fixed  beneath  the  floor  of  the  cage,  in  Avhich  the  cut  end 
was  placed.  By  renewing  the  twig  with  sufficient  frequency  the  natural 
feeding  conditions  of  the  insect  could  be  closely  followed. 

Fig.  3  -hows  one  of  these  normal  atmosphere  cages  in  operation.  In 
the  muslin-bag  cages  which  were  tied  over  branches  in  the  orchards? 
outdoor  conditions  woe  perhaps  somewhat  more  nearly  attained.  The 
result:-  obtained  in  these  two  kinds  of  cages  closely  approximated  each 
other,  so  it  is  fair  to  conclude  that  the  normal  life  history  of  the  insect 
has  been  practically  determined.  Fig.  5  gives  a  very  fair  idea  of  the 
appearance  of  the  muslin-bag  cage 


THE   CALIFORNIA   TUSSOCK-MOTH.  197 

A  series  of  breeding  cages,  started  March  17  with  newly  hatched 
larvae,  will  illustrate  the  results  obtained  by  laboratory  methods.  The 
notes  show  the  following  data: 

Mar.  17— Eggs  hatched. 

27 — One  entering  somnus. 
29— One  molting. 
Apr.    2— The  last  one  entering  somnus. 

5 — One  entering  second  somnus. 

6 — The  last  one  molting. 

7— One  passing  second  molt. 
13— The  last  one  entering  second  molt. 
15 — One  entering  third  somnus. 
17 — The  last  one  passing  second  molt. 
20  -One  passing  third  molt. 
22 — The  last  one  entering  third  somnus. 
26— The  last  one  passing  third  molt. 
28 — One  entering  fourth  somnus. 
May    1— One  passing  fourth  molt. 

3 — The  last  one  is  in  fourth  somnus. 

6— One  spinning  up. 

7— Last  one  passing  the  fourth  molt. 
21 — First  male  has  emerged. 
23 — The  last  one  spinning  up. 
June    4 — First  female  has  emerged. 

7 — Last  female  has  emerged. 
12 — Last  male  has  emerged. 

In  explanation  of  the  above  it  should  be  said  that  the  somnus  is  the 
resting  condition  entered  into  preceding  each  change  of  skin;  the  molt 
the  close  of  the  somnus,  and  the  insect  soon  thereafter  begins  to  feed; 
spinning  up  is  the  formation  of  a  cocoon.  After  cocoon  is  made  there 
is  a  somnus  of  about  two  days,  and  then  the  insect  becomes  a  pupa  and 
finally  the  adult  insect  emerges. 

Putting  the  data  above  in  another  form,  the  length  of  time  occupied 
in  passing  each  feeding  stage  and  somnus  for  the  slowest  and  the  most 
precocious  is  as  follows: 

First  Last 

Insect.  Insect. 

First  stage 8  days  15  days 

soninus 2  days    •     4  days 

Second  stage 7  days  7  days 

somnus 2  days  4  days 

Third  stage 8  days  5  days 

somnus 5  days  4  days    • 

Fourth  stage 8  days  7  days 

somnus 3  days  3  days 

Fifth  stage  . 5  days  16  days 

In  cocoon 15  days  20  days 

The  first  cocoon  was  produced  in  forty-eight  days,  the  last  in  sixty- 
five;  the  first  male  moth  in  sixty-two  days,  the  last  in  eighty-five.  The 
average  of  the  males  was  about  seventy-five  days  from  the  hatching  of 
the  egg;  the  average  for  the  females  was  about  seventy-eight  days. 


198  UNIVERSITY   OF    CALIFORNIA 


EX  PER I M EXT    STATION. 


The  orchard  experiments  may  be  represented  by  the  cage  bearing  our 
laboratory  number  13,  an  account  of  which  is  as  follows:  A  large 
number  of  tussock-moth  larvae  just  hatched  were  placed  on  a  Newtown 
Pippin  branch  inclosed  in  a  muslin  bag.  A  considerable  variability 
was  noted  in  this  experiment.  All  the  larvae  were  hatched  at  about 
the  same  time  (March  29);  by  April  6  a  great  difference  in  size  was 
noted:  by  April  10  some  had  emerged  from  the  first  molt,  but  the 
majority  had  not  emerged  until  April  12.  On  April  21  practically  all 
had  emerged  from  the  second  molt,  and  some  were  entering  the  third, 
but  a  few  were  still  in  the  third  molt  May  5.  On  May  7  some  had 
entered  the  fourth  molt,  and  on  May  11  some  had  emerged  from  the 
fourth  molt,  and  one  male  was  spinning  up.  A  few  were  still  in  the 
fifth  larval  stage  June  2.  So,  while  the  average  length  of  larval  life 
history  was  fifty-five  days,  some  have  required  more  than  sixty-seven 
days  to  reach  the  pupa  stage. 

The  average  period  occupied  by  these  insects  noted  during  the  course 
of  the  experiments  is  as  follows: 

First  stage 11  days 

somnus 2  days 

Second  stage 6  days 

somnus 3  days 

Third  stage  .__ ___ 6  days 

somnus 2  days 

Fourth  stage 9  days 

somnus 3  days 

Fifth  stage 12  days 

In  cocoon   24  days 

It  will  be  seen  on  comparing  the  above  with  the  corresponding  table 
that  the  results  obtained  in  the  laborator}'  breeding  cages  are  quite 
closely  alike.  It  was  also  brought  out  by  these  experiments  that  the 
length  of  the  larval  life  differed  with  the  sex,  being  about  55  to  65  days 
for  females,  while  the  males  require  only  50  to  55  days  to  reach  the 
3pinning-up  stage. 

HABITS. 

On  hatching,  the  young  larvae  remain  clustered  over  the  egg  mass 
until  they  have  gained  their  normal  nearly  black  color,  which  may 
require  two  or  three  days.  In  the  meantime,  they  appear  to  be  feeding 
on  the  materia]  which  holds  the  eggs  together.  Those  larvae  which 
hatch  in  the  interior  of  the  egg  mass  necessarily  have  to  burrow  their 
way  out  through  this  tough  binding  substance,  and  the  mass  eventually 
appears  riddled  with  these  punctures. 

This  hatching  occurs  in  the  orchards  about  the  time  the  new  leaves 
are  expanding;  but  there  is  a  great  variability  in  the  time  of  hatching, 
some  emerging  early  in  February,  while  others  are  still  hatching  as  late 
as  April  or  even  May. 


THE    CALIFORNIA    TUSSOCK-MOTH. 


199 


After  the  larvae  leave  the  egg  mass  they  wander  to  the  near-by  buds 
and  commence  feeding.  This  early  feeding  is  in  the  form  of  minute 
punctures  in  the  youngest  leaves  and  blossoms,  and  the  young  leaf  stems 
are   also  attacked.     As  the   larvae  grow  older  they  still    retain    their 


FIG.  6.    Tussock-moth  larva.    About  one-half  larger  than  natural  size. 

habit  of  burrowing  into  the  fleshy  tissue,  and  so  do  much  damage  to  the 
young  fruit.  They  become,  however,  more  and  more  leaf  feeders  as 
time  advances,  and  the  older  insects  do  little  damage  to  the  fruit. 


FIG. 


7.    The  same  larva  as  in  Fig.  6,  with  hairs  removed  to  show  color  and 
structure  of  the  body. 


The  larvae  feed  at  all  times  of  the  day  and  are  not  gregarious  in 
habits;  those  from  one  nest  will  become  very  generally  distributed  over 
the  tree  before  the  larval  life  is  complete. 

The  molts  are  passed  in  more  or  less  protected  places,  often  on  the 
under  side  of  the  leaves.  Before  molting,  the  larvae  spin  a  thin  carpet 
of  silk  on  the  surface  where  they  expect  to  remain  during  the  molt. 
The  molt  is  accomplished  by  a  circular  break  near  the  head;  the  larvae 


FIG.  S.    Tussock-moth  cocoon  masses  on  the  trunks  and  limbs. 


FK».  9.    Mass  of  cocoons  of  the  tussock-moth.    Some  of  the  cocoons  have 
been   torn   open,  revealing    pupae  of   both    sexes     (About   two-thirds 

natural   :-.iz<-  ) 


THE   CALIFORNIA   TUSSOCK-MOTH. 


201 


crawl  out  of  the  old  skins  and  remove  the  head  shell  later.  While  the 
larva^  are  normally  quiescent  for  some  time  preceding  the  molts,  they 
are,  however,  able  to  walk  if  disturbed,  and  may  change  their  position 
before  emerging. 

The  larger  larvae  often  assume  a  wandering  habit,  which  causes  them 
to  leave  the  original  food  plant  and  seek  others,  sometimes  at  a  consid- 
erable distance  away.     Isolated  larvae  are  often  found  on  young  trees 


FIG.  10.    Tussock-moth  cocoons  on  smaller  twigs. 

several  hundred  feet  from  a  nest.  It  is  possible,  also,  that  the  very 
young  insects  may  have  been  carried  by  the  wind  and  birds  and  so  aid 
in  the  general  distribution.  As  the  female  moth  is  wingless,  the  distri- 
bution of  the  species  must  take  place  exclusively  in  the  earlier  stages. 
When  the  larva?  are  fully  developed  they  select  somewhat  protected 
places  on  the  trunks  of  trees  and  the  under  side  of  branches,  where 
they  spin  up  sometimes  in  masses  of  cocoons;  when  the  caterpillars 
are  very  numerous,  these  masses  may  be  plastered  over  the  trunk  in 
the  form  of  a  blanket  several  inches  wide.     Fig.  8  shows  several  of 


20* 


UNIVERSITY    OF    CALIFORNIA  — EXPERIMENT   STATION 


these  blankets  on  the  trunk  and  large  limbs  of  an  apple  tree.  Fig.  9  is 
a  view  of  one  of  these  masses  taken  against  a  white  cloth.  A  close  inspec- 
tion of  this  illustration  will  show  the  pupa?  of  male  and  female  tussock- 
moths  protruding  from  the  cocoons,  which  have  been  torn  open  in 
removing  them  from  the  tree  trunk.  As  the  males  spin  up  first  they 
often  form  masses  by  themselves,  the  females  spinning  their  cocoons 
elsewhere. 

The  caterpillars  sometimes  also  spin  up  on  the  under  side  of  bunches 
of  leaves  at  the  end  of  small  twigs.  The  leaves  are  then  securely 
webbed  to  the  twig  by  the  caterpillars  before  the  cocoons  are  spun. 
Some  of  these  cocoons  are  shown  in  Fig.  10.     The  spinning-up  habits  of 

the  caterpillar  then  result  in  a  general 
distribution  of  the  cocoons  over  the 
surface  of  the  tree,  as  well  as  large 
masses  on  the  trunks,  and  also  on 
fences  and  other  suitable  objects  in  the 
vicinity. 

When  the  moths  emerge  the  males 
lly  about  in  search  of  receptive 
females.  The  females  have  a  greatly 
developed  abdomen  filled  with  eggs. 
The  legs  are  fairly  well  developed, 
but  the  wings  are  rudimentary  and 
unadapted  for  flight.  The  female  is 
so  heavy  that  it  makes  little  effort  to 
crawl  about,  but  usually  remains 
clinging  to  the  mass  of  cocoons  from 
which  it  has  emerged.  Here  it  also 
deposits  the  egg  mass,  usually  attached 
to  the  cocoons,  but  sometimes  is  directly  cemented  down  to  the  twig. 
The  laying /of  the  eggs  takes  place  in  a  very  few  days  after  emergence. 
The  males  are  supposed  to  be  attracted  by  the  odor  of  the  females, 
and  will  go  considerable  distances  to  find  isolated  insects.  They  have 
often  been  noted  attempting  to  gain  entrance  to  the  muslin-bag  cages 
where  the  females  had  emerged. 

Mating  may  take  place  at  once  after  the  female  has  emerged,  or  a 
'.•oi;:-dderable  time  may  elapse.  The  eggs  are  often  laid  within  an  hour 
or  two  thereafter.  While  laying  eggs  the  female  remains  stationary, 
building  up  the  mass  by  moving  the  tip  of  the  abdomen  to  and  fro. 
The  eggs  are  deposited  in  a  fibrous  cementing  material,  which  com- 
plete] v  covers  them  and  holds  the  mass  together  very  firmly,  and  also 
make-;  a  strong  attachment  to  the  body  against  which  the  mass  is 
deposited.  As  the  eggs  are  ejected  the  abdomen  of  the  moth  slowly 
contracts,  making  t he  insect  very  much  smaller  than  it  was  before  the 
laying  commenced. 


FIG.  11. 


Female  moths  just  emerged  and 
resting  on  cocoons. 


THE   CALIFORNIA   TUSSOCK-MOTH.  203 

The  males  fly  during  the  clay  and  also  in  the  evening,  or  possibly  all 
night  when  the  weather  conditions  are  favorable. 

The  larva?  and  female  adults  are  remarkably  hardy.  The  caterpillars 
can  withstand  long  periods  of  starvation  and  will  develop  in  confine- 
ment under  conditions  which  would  kill  many  other  insects.  Some 
larvae  developed  from  eggs  in  a  Mason  jar  with  the  lid  closed  down, 
their  food  for  the  most  part  being  a  rotten  apple;  but  this  diet  was 
varied  at  times  with  some  apple  leaves  sprayed  with  arsenate  of  lead. 

Another  interesting  fact  about  the  larvae  is  their  apparent  sense  of 
direction,  for  when  beaten  from  the  trees  they  lose  very  little  time  in 
finding  their  way  back  to  the  trunk.  This  ability  to  find  the  trunk  of 
the  tree  seems  to  be  due  probably  to  vision,  as  any  object  such  as  a 
post  standing  erect  will  attract  them.  That  the  finding  of  the  tree 
trunks  is  not  due  to  accident  can  be  readily  seen,  for  when  the 
caterpillars  are  shaken  from  the  trees  they  soon  form  into  lines  which 
converge  at  the  trunk,  and  only  a  few  can  be  found  aimlessly  wander- 
ing about. 

NATURAL    ENEMIES. 

As  this  caterpillar  is  a  native  of  California,  we  might  expect  it  to 
have  parasitic  and  predaceous  insect  enemies,  as  well  as  diseases. 

Some  experiments  were  undertaken  with  the  idea  of  determining 
these  as  far  as  possible.  The  method  of  procedure  was  to  collect 
specimens  in  the  field  at  various  dates  and  stages  of  development  and 
keep  them  for  the  remainder  of  their  period  of  development  in  muslin- 
bag  cages  tied  over  apple  branches.  It  was  thought  that  this  would 
prevent  any  infestation  by  parasites  after  the  date  of  collection. 

There  were  in  all  fifteen  of  these  experiments,  the  dates  of  collection 
ranging  from  March  24  to  April  26.  The  data  obtained  are  embodied 
in  the  table  below,  from  which  it  will  be  seen  that  no  parasitization 
occurred  until  April  11.  All  the  collections  made  after  that  date  con- 
tained parasitized  larva?. 

The  only  parasites  obtained  in  these  experiments  were  Tachina  flies. 
These  parasitic  flies  resemble  in  general  appearance  the  house  fly,  but 
most  of  them  are  larger. 

In  addition  to  the  collections  of  larva?,  a  number  of  collections  were 
made  after  spinning-up  had  occurred.  These  were  kept  in  paper  bags 
in  the  laboratory.  All  the  pupa  collections  showed  a  liberal  percentage 
of  parasitization,  in  some  cases  as  high  as  fifty  per  cent.  The  majority 
of  the  parasites  taken  were  the  same  kind  of  Tachina  flies  obtained 
from  larvae,  but  the  pupa  collections  also  showed  several  species  of 
Ichneumon  flies  and  other  parasitic  wasps.  There  is  also  a  Chalcid 
parasite  which  develops  in  the  larvae  and  kills  them  before  they  reach 
the  spinning-up  stage.  In  this  case  the  parasitized  caterpillar  remains 
fastened  to  the  leaf  or  twig  on  which  it  dies  and  the  adult  larvae 
of  the  parasite  emerge  from  the  caterpillar  and   pupate  in  a  row  on 


204 


UNIVERSITY   OF    CALIFORNIA— EXPERIMENT   STATION. 


each  side  of  the  parasitized  insect.     Twenty  to  thirty  parasites  develop 
from  a  single  larva. 

There  is  but  little  evidence  of  predaceons  insect  attack  on  this  cater- 
pillar or  of  it  serving  to  any  extent  as  food  for  birds. 

The  eggs  are  attacked  by  a  minute  hymenopterous  parasite  (Telenomus 
orgy  la  Ash).  This  looks  like  a  very  small  gnat,  and  is  found  crawling 
over  the  egg  masses.  The  larvae  of  this  parasite  develop  within  the 
ggs  of  the  tussock-moth  and  begin  to  emerge  early  in  the  spring.  The 
emergence  of  the  parasite  continues,  however,  until  after  new  egg 
masses  have  been  deposited. 

The  egg  masses  are  also  attacked  by  the  larvae  of  a  Dermestid  beetle. 
This  larva  is  brownish  colored  and  covered  with  long  hairs;  it  is  able 
to  crawl  rather  rapidly,  but  may  remain  still  if  disturbed. 

The  egg  parasite  and  the  Dermestid  beetle  are  the  most  useful  parasites 
of  the  tussock-moth,  as,  by  attacking  the  eggs,  they  prevent  the  cater- 
pillars from  hatching,  the  efficiency  depending  on  the  abundance  of  the 
parasitization.  The  other  parasites  attack  the  larvae  only  after  they 
have  developed  and  completed  their  injurious  attacks  on  the  fruit  and 
leaves. 

While  parasites  have  been  very  abundant  they  have  not  destroyed  more 
than  fifty  per  cent  of  the  caterpillars,  many  moths  having  emerged 
and  deposited  their  egg  masses.  So,  if  the  egg  parasite  and  Dermestid 
beetle  do  not  become  much  more  abundant,  or  some  other  cause  of 
death  intervene,  there  will  be  a  liberal  infestation  of-  the  orchards  again 
next  season. 

Diseases  were  scarcely  at  all  in  evidence  among  the  larvae.  A  few 
Larvae  died  early  in  April,  apparently  from  a  bacterial  disease,  but  cater- 
pillars forced  to  feed  on  leaves  wet  with  water  containing  an  infusion 
of  the  dead  bodies  did  not  result  in  infection.  Three  of  these  experiments 
were  tried. 

The  following  table  gives  the  breeding-cage  records  of  parasitization: 


Date. 

Orchard. 

Egg  Masses 
Obtained. 

Death  Without 

Reproduction. 

Not  Parasitized. 

Parasitized. 

Male 

Female. 

March  24                         

Eaton 

Eaton...:. 
Eaton  

4 
14 

4 
5 

0 

Mar.),  24 

March  25                                                

0 

0 

March  25           - 

Eaton 

Eaton 

Eaton 

Eaton 

Tuttle 

Tuttle 

Eaton   

Eaton 

Eaton 

Judd 

Campbell  . 

Eaton 

Eaton 

2 
4 
7 
11 
9 
4 
2 

27 
15 
10 

2 

6 
9 
4 
13 
7 
4 

0 

.  31 

\prj]       2                                             

0 

0 

Ma  rch  30                          

0 

2 

April       fr> 

April     ii                                             

"l ""' 

0 
0 
2 

\pril     12           

7 
4 
8 

5 

22   

April    26 

..     28 

14... 

14 

5 

9 
9 

5 
6 

3 

1 

THE   CALIFORNIA   TUSSOCK-MOTH.  205 

It  will  be  seen  by  referring  to  the  above  table  that  a  number  of 
females  failed  to  reproduce  ;  that  is,  they  died  either  in  the  pupa  case 
or  shortly  after  emergence  without  laying  eggs.  In  all  of  these  cases 
the  cuticle  of  the  abdomen  was  partly  rotted  away,  exposing  the  eggs. 
This  disease  in  some  cases  killed  over  fifty  per  cent  of  the  females, 
while  the  males  almost  invariably  emerged. 

While  the  natural  enemies  of  the  tussock-moth  caterpillar  are  not 
to  be  depended  upon  to  control  the  insect  year  after  year,  yet  it  is 
evident  that,  due  to  their  irregular  action  or  to  some  other  cause  equally 
uncertain  in  its  action,  a  great  variability  in  abundance  is  brought 
about.  An  instance  of  sporadic  increase  came  under  our  notice  in  the 
fall  of  1903,  when  the  lupins  along  the  beach  of  Monterey  Bay  in  the 
vicinity  of  Port  Rogers  were  very  badly  infested,  but  the  insect  has  not 
been  abundant  there  since.  Examinations  in  that  region  during  the 
past  two  seasons  have  shown  that  the  egg  masses  were  very  largely 
destroyed  by  the  Dermestid  beetle,  before  referred  to,  and  that  the  egg 
parasite  is  also  abundant.  Other  parasites  are  also  in  evidence,  and 
this  parasitization  may  account  for  the  greatly  decreased  numbers  of 
the  caterpillars  along  the  beach. 

This  insect  has  also  experienced  a  similar  rise  and  fall  in  abundance 
in  the  apple  orchard,  having  almost  disappeared  during  a  long  period 
of  years  preceding  1903.  Whether  or  not  the  tussock  caterpillar  will 
be  a  serious  pest  in  1907  can  only  be  a  matter  of  conjecture,  for,  as  has 
already  been  stated,  the  eggs  have  been  laid  and  only  their  destruction 
by  natural  or  artificial  means  can  prevent  an  abundant  hatching  of 
young  caterpillars  in  the  spring. 

POISONING    EXPERIMENTS. 

The  fact  that  the  tussock  caterpillar  is  not  readily  poisoned  by  arseni- 
cals  has  been  alluded  to  in  the  opening  paragraphs  of  this  bulletin.  It 
was  hoped,  however,  that  some  method  of  application  might  be  discov- 
ered which  would  prove  successful  as  a  means  of  control. 

Some  laboratory  experiments  were  conducted  in  1905  with  this  end  in 
view,  and  it  was  found  that  the  newly  hatched  larvae  were  more  readily 
poisoned  than  the  more  mature  insects. 

Arsenate  of  lead  was  the  material  experimented  with.  When  the 
foliage  was  thoroughly  covered  with  this  insecticide  applied  at  a  dilu- 
tion of  3  to  6  pounds  to  50  gallons  of  Avater  (the  wet  weight  of  the 
material  as  taken  from  the  keg),  and  newly  hatched  larvae  were  placed 
upon  it,  the  majority  of  them  died  from  arsenical  poisoning;  but  even 
then  some  survived  and  only  succumbed  after  prolonged  exposure  to 
thoroughly  poisoned  leaves.  Slightly  older  insects  were  found  to  be 
extremely  resistant ;  some  survived  four  weeks,  when  their  only  food 
was  leaves  literally  whitewashed  with  arsenate  of  lead.     These  larvae 


206 


UNIVERSITY    OF    CALIF*  >RNIA— EXPERIMENT   STATION. 


ate  but  little,  and  doubtless  died  from  the  combined  effects  of  starva- 
tion and  arsenical  poisoning.  It  was  then  evident  that  even  early 
spraying  with  heavy  doses  of  arsenate  of  lead  might  not  prove  success- 
ful, for.  added  to  the  resistance  of  the  insects  would  be  the  difficulty  of 
keeping  the  rapidly  expanding  foliage  covered  with  poison.  The  feed- 
ing habits  of  the  young  caterpillar  were  also  against  success,  as  they 
worked  largely  on  the  buds  and  blossom  clusters,  which  were  very  diffi- 
cult to  cover  with  spray.  Also,  the  frequent  rains  that  occur  in  the 
early  spring  tend  to  render  spraying  ineffective  ;  and  last,  but  not  the 


F[('j.  12.     Foliage  sprayed  with  arsenate  of  lead  for  very  young  larvae  of  the  tussock-moths. 

Least  important,  the  prolonged  period  of  hatching,  which  covers  nearly 
four  months,  is  against  the  success  of  such  a  spraying  campaign. 

Notwithstanding  all  the  apparent  difficulties,  some  early  spraying 
experiments  were  undertaken  this  spring,  notably  in  orchards  of  Messrs. 
M.  B.  Tuttle  and  R.  W.  Eaton.  Spraying  began  in  the  Tuttle  orchard 
on  March  8.  and  continued,  owing  to  delays  caused  by  the  rain,  for 
about  three  weeks.  Arsenate  of  lead  was  used  at  the  rate  of  3  pounds 
to  50  gallons  of  water,  and  the  trees  were  thoroughly  sprayed.  The 
pillar-  were  hatching  abundantly  at  this  time,  and  there  were 
also  •<*.  great  number  of  larva3  which  had  passed  the  first  and  even  the 
second  molt.     Spraying  in  the  Eaton  orchard  was  not  commenced  until 


THE   CALIFORNIA   TUSSOCK-MOTH.  207 

March  29.  Here  5-5-50  Bordeaux  was  used,  with  3  pounds  of  Swift's 
arsenate  of  lead  to  50  gallons  of  the  mixture.  The  trees  were  still  in 
blossom  at  this  date  and  the  tussock-moth  larvae  were  yet  hatching 
abundantly,  but  many  of  them  were  in  more  advanced  stages  than 
when  spraying  was  commenced  in  the  Tuttle  orchard.  The  spray  was 
thoroughly  applied  in  each  case  and  many  young  larvae  were  killed, 
but  the  treatment  did  not  obviate  the  necessity  of  beating  the  trees 
several  times  later,  in  order  to  prevent  their  defoliation,  and,  in  spite 
of  all  efforts,  the  fruit  was  badly  damaged. 

PARIS    GREEN    DUSTING    EXPERIMENTS. 

Mr.  A.  N.  Judd  had  been  experimenting  with  a  "mixture  of  sulfur, 
paris  green,  hydrated  lime,  and  powdered  Milestone,  applied  with  a 
dust  blower.  The  results  led  him  to  believe  that  his  mixture  was  of 
special  value  as  a  remedy  for  the  tussock  caterpillar.  Paris  green  was 
probably  the  most  effective  ingredient,  but  in  order  to  determine  this  the 
experiments  recorded  below  were  tried. 

EXPERIMENT  1.     Paris  green 1  part 

Hydrated  lime 20  parts 

Bluestone 4      " 

Total.. 25     " 

After  one  week  several  worms  were  found  dead;  many  others  much 

shrunken.     Examined  again  in  June,  one  male  had  emerged  and  one 

pupated;  others  had  died  in  larval  stage. 

EXPERIMENT  2.     Paris  green 1  part 

Sulfur 4  parts 

Hydrated  lime 20     " 

Total 25     " 

After  one  week  several  worms  were  found  dead;  many  had  eaten  but 
little.     Examined  again  in  June,  all  were  found  dead  in  the  larval  stage. 

EXPERIMENT  3.     Paris  green 1  part 

Hydrated  lime J 24  parts 

Total _.  25     " 

After  one  week  several  worms  were  found  dead.  Examined  again  in 
June,  one  male  had  reached  pupa  stage,  but  was  very  small,  and  all  the 
others  died  in  the  larval  stage. 

EXPERIMENT  4.     Paris  green 1  part 

Hydrated  lime 16  parts 

Sulfur 4     " 

Bluestone 4     " 

Total 25     " 

After  one  week  several  were  found  dead,  others  had  eaten  little. 
Examined  again  in  June,  all  were  found  dead  in  the  larval  stage. 


208  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT   STATION. 

The  applications  were  made  to  small  branches  with  an  insect  powder 
gun  and  the  leaves  were  very  thoroughly  covered.  These  branches 
were  then  inclosed  in  muslin  bags,  along  with  a  number  of  large-sized 
tussock-moth  larva\  On  referring  to  the  table,  it  will  be  seen  that  the 
results  were  practically  the  same  in  all  the  experiments,  showing  that 
pans  green  is  the  effective  portion  of  the  mixtures.  An  experiment  was 
also  tried  with  a  mixture  of  sulfur,  hydrated  lime,  and  bluestone; 
but  in  this  case  the  larvae  all  survived  and  were  apparently  as  healthy 
as  if  feeding  on  untreated  foliage. 

Under  the  protection  of  the  bags  the  dust  mixtures  remained  on  the 
foliage  for  a  long  time,  but  some  applied  at  the  same  time  to  unpro- 
tected branches  was  soon  removed  by  the  action  of  the  wind.  The 
foliage  in  the  bag's  was  also  somewhat  injured. 

It  is  apparent,  then,  that  while  this  concentration  of  paris  green, 
thoroughly  applied,  is  capable  of  killing  even  large-sized  tussock-moth 
larva?  when  the  foliage  is  kept  covered,  the  practical  difficulties  in  the 
way  of  its  use  are  numerous.  The  loss  of  the  dust  through  the  motion 
of  the  leaves  in  the  wind  is  probably  the  worst  difficulty,  also  the  newly 
expanding  foliage  would  have  to  be  kept  covered.  With  a  dust  blower, 
however,  it  is  possible  to  go  over  an  orchard  rapidly,  and  the  applica- 
tions might  be  repeated  every  three  or  four  days  from  the  first  of  March 
to  the  middle  of  April.  It  would  be  dangerous  to  continue  the  treat- 
ment later  than  April  15,  on  account  of  the  foliage  injury.  If  such  a 
program  were  carried  out  it  would  doubtless  result  in  the  killing  of  a 
large  number  of  tussock-moth  larva?. 

The  dust  mixtures  used  by  Mr.  Judd  contained  3  pounds  of  paris 
green  to  50  pounds  of  hydrated  lime,  or  1  pound  of  paris  green  to  16.6 
pounds  of  lime.  The  mixture  used  in  our  experiments  consisted  of  one 
part  of  paris  green  to  12  parts  of  the  dilutent. 

OTHER  EXPERIMENTS  WITH  STOMACH  POISONS. 

While  the  arsenicals  are  the  only  substances  with  which  there  is  a 
reasonable  hope  of  success,  yet  some  experiments  were  tried  with  other 
poisons,  such  as  phosphorus  and  cyanides.  These  experiments  gave 
only  negative  results,  the  failure  being  in  a  large  measure  due  to  the 
difficulty  of  retaining  these  poisons  in  an  active  form  when  spread  over 
apple  foliage  in  a  finely  divided  condition. 

CONTACT    INSECTICIDES. 

The  tussock  caterpillar,  owing  to  its  protection  of  hairs,  is  very  diffi- 
cult to  wet  with  a  spray,  and  so  the  use  of  the  contact  insecticide  offers 
little  hope  for  success.  It  was,  however,  advisable  to  try  such  sprays. 
Two  contad  spray  experiments  were  tried  in  the  Eaton  orchard  March 


THE   CALIFORNIA   TUSSOCK-MOTH.  209 

27,  1906.  These  consisted  of  a  five  per  cent  mechanical  mixture  of 
kerosene  oil,  and  whale-oil  soap.  The  whale-oil  soap  mixture  consisted 
of  1  pound  to  7  gallons  of  water,  with  the  extract  from  1  pound  of 
quassia  chips  added.  Fifty  gallons  of  each  spray  were  applied.  A 
power  outfit  with  a  rapid  agitator  was  used,  and  the  spraying  was  done 
with  fair  thoroughness,  although  the  men  handling  the  nozzle  were 
new  at  the  work. 

As  a  result  a  few  specimens  were  found  to  be  killed  with  the  whale-oil 
soap,  but  the  kerosene  was  apparently  harmless,  and  in  neither  case  was 
a  practical  efficiency  obtained.  Later  some  experiments  were  tried 
with  pyrethrum  applied  as  a  spray  and  a  strong  soap  solution  (common 
laundry  soap).  The  pyrethrum  was  ineffective.  The  soap  solution 
killed  about  fifty  per  cent  of  the  larvae,  but  it  later  caused  most  of  the 
foliage  to  fall. 

These  experiments  are  sufficient  to  illustrate  the  futility  of  the  use 
of  such  contact  insecticides  as  are  now  known. 

DAMAGE    DUE    TO    THE    TUSSOCK-MOTH    CATERPILLAR. 

While  this  insect  may  become  so  abundant  as  to  defoliate  the  trees 
and  so  destroy  the  crops  for  one  season  and  partly  for  the  next  also, 
yet  these  severe  attacks  are  rather  rare.  The  great  general  injury  due 
to  this  insect  is  sustained  by  the  fruit. 

Almost  from  the  first  the  young  caterpillars  show  a  decided  tendency 
to  eat  into  the  newly  formed  fruit.  They  often  begin  before  the  blos- 
soms have  opened  and  continue  until  the  larvae  are  half  grown.  The 
mature  larvae  are  more  strictly  leaf-feeders. 

Some  varieties  of  apples  are  much  more  severely  attacked  than 
others,  notably  Newtown  Pippins  and  Bellflowers.  The  injury  sus- 
tained by  the  fruit  varies  from  a  shallow  surface  abrasion  to  a  deep 
excavation,  sometimes  extending  to  the  core.  This  injured  fruit  gener- 
ally remains  on  the  tree  and  the  wound  heals  over,  becoming  covered 
with  scar-like  tissue.  When  severely  bitten  the  apples  are  much  dis- 
torted and  have  to  be  culled  out,  thus  often  resulting  in  a  considerable 
loss  to  the  producer. 

Reference  to  table  on  page  192  will  show  that  the  total  injured  fruit 
may  run  as  high  as  seventy  per  cent.  It  is  not  all  necessarily  a  total 
loss,  as  some  may  be  sold  as  seconds. 

SUGGESTIONS    FOR    CONTROL    MEASURES. 

Spraying. — Spraying  with  arsenicals  has  so  far  proved  unsatisfactory, 
and  therefore  should  not  be  depended  upon.  Contact  sprays  are  like- 
wise ineffective,  and  none  of  the  winter  washes  can  be  of  any  material 
value,  as  the  eggs  are  almost  impregnable  to  such  treatment. 


UNIVERSITY    OF    CALIFORNIA  — EXPERIMENT   STATION 


Picking  the  Egg  Masses. — The  egg  masses  are  nearly  spherical  bodies, 
grayish  brown  in  color,  and  average  somewhat  over  a  fourth  of  an  inch 
in  diameter.  They  arc  therefore  very  readily  seen.  The  search  for 
eggs  is  facilitated  by  the  fact  that  they  are  usually  laid  on  the  cocoons, 
and  when  these  are  on  the  small  branches  and  twigs  the  dead  leaves 
secured  to  the  twig  by  the  web  spun  by  the  caterpillar  also  help  to  locate 
the  eggs. 

Egg  picking  should  commence  as  soon  as  the  leaves  fall  in  the 
autumn,  as  the  eggs  are  easier  seen  at  that  time  than  after  they  have 
become  brown  by  weathering  over  winter.     It  often  happens,  also,  that 

the  thorough  clean- 
ing of  an  orchard 
requires  a  consider- 
able time,  and  it  is 
important  to  finish 
before  the  caterpil- 
lars begin  hatching. 
To  be  successful 
the  egg-picking  oper- 
ation must  be  per- 
formed with  great 
thoroughness.  It  is 
necessary  to  remove 
not  only  the  egg 
masses  deposited  on 
the  larger  limbs,  but 
those  scattered  over 
the  small  branches 
and  twigs  as  well. 
In  performing  this 
work  the  men  should 
use  ladders  of  sufficient  height  to  enable  them  to  reach  the  tops  of  the 
trees.  The  thorough  removal  of  the  egg  masses  is  trying  work  and  the 
men  employed  are  likely  to  grow  indifferent  to  the  task,  unless  they  are 
thoroughly  impressed  with  the  necessity  of  finding  the  very  last  one  on 
the  tree.  Even  with  the  most  conscientious  work,  some  eggs  will  be 
Left,  especially  on  large  trees,  and  it  has  been  found  that  three  pickings 
will  still  leave  eggs. 

As  it  is  the  Last  few  egg  masses  that  count,  some  system  which  will 

enable  one  to  remove  these,  as  far  as  possible,  is  desirable.     It  is  sug- 

ed   that  the  men  carry  a  small  can  of  whiting  and  a  paint  brush 

with  them,  and  as  the  limbs  are  examined  they  may  be  marked.     The 

tem   to  follow  would  be  to  mark  a  principal  branch  at  the  base  of 

the  tree  and  then,  proceeding  upward,  mark  the  laterals  as  fast  as  they 


FIG.  13.  Larvae  of  tussock-moth  feeding  on  apple  foliage  and  fruit. 


THE    CALIFORNIA   TUSSOCK-MOTH. 


211 


are  examined.  The  marking  program  should  be  followed  out  to  the 
small  branches  which  give  rise  to  the  fruit-bearing  spurs.  The  mark 
had  best  be  a  ring  painted  completely  around  the  branch,  so  that  it 
may  be  seen  from  all  points  of  observation.  Of  course  the  branches 
should  be  observed  from  all  sides,  as  the  eggs  are  likely  to  be  concealed 
anywhere.  Further  precaution  should  be  taken  in  insisting  that  the 
egg  masses  be  completely  removed,  since  a  few  eggs  are  liable  to  be  left 
attached  to  the  stems  if  this  part  of  the  work  is  not  thoroughly  done. 

Such  a  system  should  obviate  the  bewildering  effect  of  the  tree  when 
viewed  as  a  whole,  and  at  the 
same  time  enable  a  man  to  go 
over  it- all  without  missing  any 
part;  and  further,  this  system 
should  enable  the  men  to  do  the 
work  thoroughly  in  one  opera- 
tion. The  cost  of  such  an  opera- 
tion should  not  be  greatly  more 
than  that  of  less  thorough 
methods,  and  when  considered 
in  the  light  of  results  the  in- 
creased returns  in  the  way  of 
uninjured  fruit  would  make  it 
less  expensive.  That  thorough 
work  pays  will  be  seen  by  refer- 
ring to  table  on  page  192.  It  will 
be  seen  that  the  injured  fruit  in 
the  Rodgers  orchard  averaged  12 
per  cent  less  than  where  the  work 
was  less  thoroughly  done.  The 
original  infestation  in  the  Rod- 
gers orchard  was  quite  as  great 
as  that  of  his  neighbors,  and  if 
he  had  not  followed  carefully 
the  egg  picking  for  two  seasons, 
large. 


FIG 


14.     Larva  below  tar  rope  band. (Cloth  strip 
was  placed  on  tree  for  photographing.) 


his  losses  would  have  been  quite  as 


The  Disposal  of  the  Eggs. — The  egg  masses  should  not  be  thrown  on 
the  ground,  for  while  this  method  may  result  in  their  destruction,  it  is 
by  no  means"  certain,  since  it  is  known  that  the  young  larvae  are  able  to 
crawl  a  considerable  distance.  Thus,  if  they  hatched  on  the  ground  in 
the  orchard,  some  would  doubtless  find  their  way  to  the  trees. 

The  men  should  carry  a  pouch  swung  over  the  shoulder,  in  which  all 
the  egg  masses  gathered  should  be  placed.  When  the  eggs  have  been 
gathered  they  may  be  destroyed  by  burning.  It  may,  however,  prove 
advisable  to  foster  the  egg  parasite  (Telenomus  orgyise)  and  the  Der- 


212 


UNIVERSITY    OF    CALIFORNIA— EXPERIMENT   STATION. 


mestid  beetle.  In  this  event  the  eggs  should  not  be  burned,  as  the 
parasites  are  also  destroyed  by  this  operation,  but  they  may  be  left  in 
open  boxes  distributed  through  the  orchards,  in  the  hope  that  the 
emerging  parasites  will  further  infest  what  egg  masses  still  remain  on 
the  trees. 

The  gathered   eggs  should  be  removed  from   the  orchard  early  in 
February  when   the  caterpillars  begin  to  hatch.     If  the  eggs  are  then 

removed  to  a  spot 
several  hundred  yards 
from  the  nearest  or- 
chard, there  is  little 
if  any  danger  of  the 
emerging  larvae  find- 
ing their  way  back  to 
the  trees.  In  storing 
the  egg  masses  they 
should  be  protected 
from  the  weather  by 
a  covering  of  boards 
and  also  raised  up  off 
the  ground. 

In  May  the  eggs 
can  be  returned  to  the 
orchard,  since  the  egg 
parasite  is  then  emer- 
ging in  force.  Some 
caterpillars  may  also 
still  be  hatching,  but 
observation  has  shown 
that  the  late  hatch- 
ings do  not  injure  the 
fruit,  and  further  that 
they  are  almost  inva- 
riably parasitized. 
The  advisability  of 
returning  the  eggs  will  be  governed  by  the  condition  of  the  orchard.  If 
the  egg-picking  operation  has  so  completely  removed  the  larvae  that 
little  or  no  damage  results,  it  may  be  well  to  give  the  collected  eggs 
to  some  less  fortunate  neighbors. 

Secondary  Measures. — After  the  caterpillars  have  been  allowed  to 
hatch  the  only  treatment  which  will  reduce  their  numbers  is  beating 
the  trees.  This  operation  should  be  commenced  early  in  April,  and, 
like  the  egg  picking,  the  degree  of  success  will  depend  on  the  thorough- 


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J 

A 

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\ 

V 

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%  4 

V 

%                                      me 

FIG.  15.    The  same  as  Figure  14,  but  enlarged. 


THE   CALIFORNIA   TUSSOCK-MOTH. 


213 


ness  with  which  the  work  is  done.  The  tree  should  be  vigorously 
thrashed,  and  in  badly  infested  orchards  three  or  four  beatings  will  be 
required  to  reduce  the  number  of  caterpillars  below  the  danger  point. 

In  order  to  prevent  the  caterpillars  from  re-ascending  the  trees  a 
sticky  band  must  be  placed  on  the  trunk.  Pine  tar,  tanglefoot  com- 
pound, or  even  crude  oil  will  make  such  a  band.  The  sticky  prepara- 
tion can  be  applied  directly  to  the  bark,  or  it  may  be  painted  on  a 
paper  band  which  has  first  been  snugly  fastened  around  the  trunk. 
Still  another  method  of  application  is  to  saturate  a  piece  of  baling  rope 
in  the  sticky  mixture  and  then  tie  it  around  the  trunk.  Any  inequali- 
ties which  hold  the  rope 
away  from  contact  with 
the  bark  may  be  filled 
with  some  burlap  or  cot- 
ton waste  dipped  in  the 
mixture. 

The  sticky  rope  band  is 
perhaps  the  best  of  all  the 
forms  that  have  been  de- 
vised, asit  is  easy  of 
application  and  does  not 
waste  the  material  as 
much  as  some  other 
methods. 

The  bands  are  effective 
as  long  as  they  remain 
sticky,  which  is  generally 
not  more  than  a  week. 
The  length  of  time  that 
these  bands  will  remain 
sticky  will  depend  on  the 
weather  conditions  and  the  material  used.  Pine  tar,  crude  oil,  and 
tanglefoot  compound  have  been  used  extensively  here.  A  tanglefoot 
mixture  can  be  prepared  by  melting  together,  with  a  gentle  heat, 
16  pounds  of  resin  and.  one  gallon  of  castor  oil.  When  the  mixture 
has  been  prepared  it  can  be  thinned  to  any  desired  consistency  by  the 
use  of  more  castor  oil. 

A  rope  band  saturated  with  this  mixture,  well  thinned  with  castor 
oil,  will  remain  effective  about  ten  days,  which  is  as  long  as  any  of  the 
sticky  band  materials  which  have  come  under  our  notice  will  last. 

Crude  oil  of  a  grade  which  is  very  rich  in  asphaltum  also  makes  a 
satisfactory  band  material,  but  there  is  some  danger  in  applying  this 
to  the  trees,  as  it  may  at  times  injure  the  bark.  A  pine  tar  and 
molasses  mixture,  using  equal  parts  of  tar  and  heavy  molasses,  has 
also  given  good  results. 


FIG.  16.    Larvae  below  fly-paper  band. 


214 


UNIVERSITY    OV    CALIFORNIA  — EXPERIMENT   STATION. 


The  use  of  the  band  may  l>e  advisable,  even  in  an  orchard  thoroughly 
egg  picked,  for  if  the  neighboring  orchards  are  not  well  attended  to 
there   may   be  a   migration  of  caterpillars  into  the  clean  orchard.     In 


FIG.  17.     Earth  cone  and  trench  used  as  a  barrier  against 
tussock-moth  larvse. 

such  a  case  the  bands  should  be  applied  early  in  April,  and  replenished 
every  ten  days  until  the  latter  part  of  May. 


SUMMARY    OF    SUGGESTIONS    FOR    CONTROL. 

Thorough  egg-picking  should  be  the  main  reliance.  As  secondary 
measures  the  use  of  bands  with  the  beating  of  the  trees,  where  enough 
caterpillars  escaped  the  egg-picking  work  to  warrant  the  expense. 
Band  the  tree   also  when  the  neighboring  orchards  are  badly  infested. 


STATION   PUBLICATIONS.  215 


STATION  PUBLICATIONS  AVAILABLE  FOR  DISTRIBUTION. 


REPORTS. 


189G.     Report    of    the    Viticulture    Work    during    the    seasons    1887-93,    with    data 

regarding  the  Vintages  of  1894-95. 
1897.     Resistant    Vines,    their    Selection,    Adaptation,    and    Grafting.      Appendix    to 

Viticultural  Report  for  1890. 
189S.     Partial   Report  of   Work  of  Agricultural   Experiment   Station   for   the  vears 

1895-9G   and    1890-97. 
1900.     Report  of  the  Agricultural  Experiment  Station  for  the  year  1897-98. 

1902.  Report  of  the  Agricultural  Experiment  Station  for  189S-1901. 

1903.  Report  of  the  Agricultural  Experiment  Station  for  1901-1903. 

1904.  Twenty-second  Report  of  the  Agricultural  Experiment  Station  for  1903-1904. 


TECHNICAL   BULLETINS— ENTOMOLOGICAL  SERIES. 


Vol.   1,  No.  1.     Wing  Veins  of  Insects. 

No.-  2.     Catalogue  of  the  Ephydridae. 


BULLETINS. 


Reprint.  Endurance  of  Drought  in  Soils  of  the  Arid  Region. 

No.  128.  Nature,  Value  and  Utilization  of  Alkali  Lands,  and  Tolerance  of  Alkali. 
(Revised  and  Reprint,  1905.) 

133.  Tolerance  of  Alkali  by  Various  Cultures. 

140.  Lands  of  the  Colorado  Delta  in  Salton  Basin,  and  Supplement. 

141.  Deciduous  Fruits  at  Paso  Robles. 

142.  Grasshoppers  in  California. 
144.  The  Peach- Worm. 

147.  Culture  Work  of  the  Substations. 

148.  Resistant  Vines  and  their  Hybrids. 

149.  California    Sugar    Industry. 

150.  The   Value  of  Oak  Leaves  for  Forage. 

151.  Arsenical   Insecticides. 

152.  Fumigation  Dosage. 

153.  Spraying    with    Distillates. 

154.  Sulfur  Sprays  for  Red  Spider. 
150.  Fowl   Cholera. 

158.  California  Olive  Oil ;   its  Manufacture. 

159.  Contribution  to  the  Study  of  Fermentation. 

100.  The  Hop  Aphis. 

101.  Tuberculosis   in   Fowls.      (Reprint.) 

102.  Commercial  Fertilizers.      (Dec.  1,  1904.) 

103.  Pear   Scab. 

104.  Poultry  Feeding  and  Proprietary  Foods.     (Reprint.) 

105.  Asparagus  and  Asparagus  Rust  in  California. 
100.  Spraying  for  Scale  Insects. 

107.  Manufacture  of  Dry  Wines  in  Hot  Countries. 

108.  Observations  on  Some  Vine  Diseases  in  Sonoma  Countv. 

109.  Tolerance  of  the  Sugar  Beet  for  Alkali. 

170.  Studies  in  Grasshopper  Control. 

171.  Commercial  Fertilizers.      (June  30,  1905.) 

172.  Further  Experience  in  Asparagus  Rust  Control. 

173.  Commercial   Fertilizers.      (December,   1905.) 

174.  A   New   Wine-Cooling  Machine. 

175.  Tomato  Diseases  in  California. 

170.  Sugar  Beets  in  the   San  Joaquin  Valley. 

177.  A  New  Method  of  Making  Dry  Red  Wine. 

178.  Mosquito  Control. 

179.  Commercial   Fertilizers.      (June,    1906.) 

180.  Resistant  Vineyards. 

181.  The    Selection   of    Seed-Wheat. 

182.  Analyses  of  Paris  Green  and  Lead  Arsenate.       Proposed  Insecticide  Law. 


216 


UNIVERSITY  OF   CALIFORNIA — EXPERIMENT   STATION. 


CIRCULARS. 


No.  1. 


9. 
10. 

11. 

12. 
13. 
15. 

i& 

17. 


Texas    Fever. 

Blackleg. 

Hog   Cholera. 

Anthrax. 

Contagious  Abortion  in  Cows. 

Remedies    for    Insects. 

Asparagus   Rust. 

Reading   Course  in   Economic 

Entomology.      (Revision.) 
Fumigation    Practice. 
Silk  Culture. 

The   Culture  of  the   Sugar  Beet. 
Recent   Problems   in   Agriculture. 

What  a  University  Farm  is  For. 
Notes   on    Seed-Wheat. 
Why     Agriculture     Should    be 

Tauaht  in  the  Public  Schools. 


No.  IS. 
19. 
20. 
21. 

22. 

23. 
24. 

25. 

26. 
27. 


Caterpillars   on   Oaks. 

Disinfection  of  Stables. 

Reading    Course    in    Irrigation. 

The  Advancement  of  Agri- 
cultural  Education. 

Defecation  of  Must  for  White 
Wine. 

Pure  Yeast  in  Wineries. 

Olive    Pickling. 

Suggestions  Regarding  Exam- 
ination   of   Lands. 

Selection  and  Preparation  of 
Vine    Cuttings. 

Marly  Subsoils  and  the  Chlo- 
rosis or  Yellowing  of  Citrus 
Trees. 


Copies  may  be  had  on  application  to  Director  of  Experiment  Statton,  Berkeley,  Gal. 


